Clear terpolymers



April l, 1958 R. J. sLocoMBE ETAL 2,829,128

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ROBERT J. SLOCOMBE GEORGE L. WEE

I N VEN T0 April l, 1958 R. J. sLocoMBE ETAL 2,829,128

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INVENToRs April 1, 1958 R. J. sLocoMBE ErAL 2,829,128

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' INVENTGRS.

April 1, 1958 R. J. sLocQMBE ET AL. 2,829,128

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y V f CLEAR TERPOLYMERS Filed Dec. 7, 1953 a lsneets.sheet 7 AYA V AVAVA v AVAVAVA C AVAVAVAVA AAVAV@ AVA April 1, 1958v R. J. sLocoMBE ET AL 2,829,128

" CLEAR TERPOLYMERS Filedneo'. 7, 1953 a sheets-sheet 8 @@@/WM/VVVV NNW/VWAM/N 'MMAA mA/WAAA/wA/vwA Ils/VENTOR.` .l

United States Patent OT CLEARk TERPOLYMERS Robert J. Slocombe, Dayton, and George L. Wesp, Englewood, Ohio, assignors to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware Application December 7, 1953, Serial No. 396,506

` 15 Claims. (Cl. 260-78.5)

This invention relates to three-component interpolymers, commonly called terpolymers, i. e., interpolymers prepared by polymerizing a monomeric mixture consisting'of three diterent monomers. In specific aspects the invention pertains to terpolymers of (a) a monomer selected from the group consisting of styrene, vinyltoluene, and `vinylxylene, (b) acrylonitrile, and (c) a monomer selected from the group consisting of dialkyl fumarate, methacrylic acid, methacrylonitrile, alkyl methacrylate, methyl vinyl ketone, monoalkyl fumarate, and monoalkyl maleate. Other aspects of the invention relate to improved methods of preparing clear terpolymers.

It is by now well known that ethylenically unsaturated monomers ditler greatly in their polymerization reactivity toward each other. There are in fact some monomers that will not undergo homopolymerization at all, i. e., polymerization of two or more molecules of the same monomer to form a polymer of that monomer, yet will readily undergo interpolymerization with certain other monomers. In terpolymerization affords a method of imparting varying characteristics to a polymer, and in many instances such characteristics cannot be obtained by mere physical admixture of two or more homopolymers. However, because of the above-mentioned differences in reactivity among monomers toward each other, marked heterogeneity is the rule in interpolymers and only under special circumstances can an interpolymer be obtained that is of sufficient homogeneity to give a trans- While some objectionable parent or clear interpolymer. properties such as color, encountered in interpolymers, can often be avoided by means such as the use of stabilizers or lower polymerization temperatures, incompatibility manifested by haze, turbidity, or opacity in plastics is not overcome by such treatment.

If a monomeric mixture is subjected to polymerization and the initial increment of polymer is segregated before the polymerization is allowed to go forward to an appreciable extent, it is frequently possible to obtain a clear interpolymer, but the commercial impracticability of such a procedure is apparent. On the other hand, if polymerization is permitted to proceed to a considerable and especially to a high degree of conversion, the more reactive monomer enters into the polymer to a greater extent than a less reactive monomer or monomers with the consequence that residual unreacted monomer becomes more and more depleted in the more reactive monomer, while the polymer being formed in the latter stages of polymerization is deficient in the more reactive monomer. made up of a variety of polymer molecules running a gamut of compositionsv such that the total polymer is heterogeneous with resultant opacity and often greatly impaired physical properties. This phenomenon, resulting in an undesirable product, can be overcome to an appreciable but limited extent by gradully adding during the course of the polymerization the more reactive monomer at a rate aimed at keeping the composition of un- There results a polymeric material which is ,l 2,829,128 Patented Apr. 1, 19,58

VICC

reacted monomeric mixture essentially constant. IAs a practical matter it is extremely difficult to approach uniformity in such an operation, and it is impossibleto use this technique at all in the case of mass (bulk) polymerization in which the polymerization reactiony mixture sets up into semi-solid or solid polymer after the reaction is only partly completed so that further access of added monomer to the total mixture cannot be obtained.

It is only in recent years that systematic laboratory and theoretical studies of interpolymerization have gone forward suiciently to permit a certain amount of predictability in this lield. It hask been theorized that in a simple binary system involving the free-radical-initiated polymerization of only two monomers, the composition of polymer will be dependent only upon the rate of four propagation steps, i. e., steps in the propagation of polymer molecules. Thus, taking a system involving two monomers, M1 and M2, a growing polymer chain can have vonly two kinds of active terminal groups, i. e., a group derivedl from M1 or a group derived from M2. Either of these groups has the possibility of reacting with either M1 or with M2. Using my and m2- to indicate these active terminal groups,-the four possible reactions are as follows:

n considerable body of experimental work has in general vfrom which it is formed.

conrmed the copolymer composition equation.

A large proportion of possible pairs of monomers are incapable, because of their respective reactivity ratios, of forming under any conditions an instantaneous polymer having the s ame composition as the monomeric mixture However there are certain monomer pairs which, in a proportion characteristic of that pair, give a copolymer having the same composition as the-particular monomeric mixture. In such instances, a batch polymerization can be carried out with a monomeric mixture of the particular composition with a resultant homogeneous copolymer containing the same relative proportions of the monomers as in the initial monomeric reaction mixture. This composition is known as the polymerization azeotrope composition, and is represented by the equation:

[Mlih-Tzml Such an azeotrope composition can exist only for those monomer pairs wherein both r1 and r2 are less thanone,

or theoretically wherein both r1 and r2 are greater than one although no examples of the latter combination are known.

While an understanding of interpolymerization involving only two monomers is now possible to a considerable extent, because of the development of the above-discussed theories, an increase in the number of monomers to three or more obviously tremendously increases the possibilities and complications. Thus, for example if 1nterpolymers of 100 monomers are to be considered, there are about 5G00 possible monomer pairs, but aboutl60,000 different combinations of three monomers are possible, and for each of these 160,000 combinations the variations in relative proportions of three monomers are infinite. If the assumptions made in the development of the copolymer composition equation still hold true where three monomers are to be interpolymerized, it is apparent that the composition `oi the terpolymers formed at any given instance will new be dependent upon the rate of nine propagation steps which are dependent upon the relative concentrations of the monomers in the monomeric mixture and the reactivity ratio between each of the pairs of the monomers in the mixture. It has been pointed out that the study of terpolymers can be simplified somewhat by application of the copolymer composition equation, suitably modified for three-component systems, so as to eliminate from consideration monomers whose ability to interpolymerize is so slight that further investigation of such combinations is obviously not warranted. However, the discovery of terpolymers having particularly desired physical properties has to the present time been limited to the needle in the haystack type ofy investigation. There is an obvious need for some procedure in the terpolymer field whereby terpolymers of particular properties can be made with a reasonable degree of predictability,

In accordance with the present invention, We have found a group of terpolymers that can be made by freeradical-initiated batch polymerization and that have the very desirable property of clarity. These terpolymers are made by polymerizing a monomeric mixture of certain proportions of three monomers. The proportions giving clear terpolymers will vary from one monomeric mixture to another depending upon the particular monomers present in that mixture. The invention is particularly applied to monomeric mixtures consisting essentially of (a) a monomer selected from the group consisting of styrene, vinyltoluene, and vinylxylene, (b) acrylonitrile, and (c) a monomer selected from the group consisting of dialkyl fumarate, methacrylic acid, methacrylonitrile, alkyl methacrylate, methyl vinyl ketone, monoalkyl fumarate, and monoalkyl maleate. For example, a monomeric mixture consisting of styrene, acrylonitrile and methyl methacrylate will, when subjected to free-radical-initiated batch polymerization, give a clear terpolymer only if the relative proportions of styrene, acrylonitrile and methyl methacrylate are properly chosen in a manner to be hereinafter described. In contrast, a monomeric mixture consisting of styrene, acrylonitrile and methacrylonitrile will give a clear terpolymer on being subjected to freeradical-initiated `hatch polymerization only if the relative proportions of the three mentioned monomers in the monomeric mixture are within certain limits which in general are different from those of the aforementioned mixtures of styrene, acrylonitrile and methyl methacrylate, and yet which are chosen in accordance with the same principle now to be discussed.

We have found that clear terpolymers of the nature described are made provided the proportions of three monomers in the monomeric mixture are chosen from the area lying along the line joining the binary polymerization azeotrope composition of the particular (a) and acrylonitrile on one hand, and the binary polymerization azeotrope composition of the particular (a) and the particular (c) on the other hand, as plotted on a triangular' coordinate graph. By Way of example, taking the case where (a) is styrene and (c) is methyl methacrylate, the point of the binary azeotrope composition of styrene and acrylonitrile is placed along one side of a triangular coordinate graph at the proper location between the apex designating percent styrene and the apex designating 100 percent acrylonitrile. This point is 76 to 77 weight percent styrene and 24 to 23 weight percent acrylonitrile. On the opposite side of the equilateral triangle, constituting the triangular coordinate graph, is placed the point representing the binary azeotrope composition of styrene and methyl methacrylate, this of course being located at the proper position on the side of the triangle between the apex representing 100 percent styrene and the apex representing 100 percent methyl methacrylate. This point is 54 Weight percent styrene and 46 weight percent methyl methacrylate. Now a straight line is drawn between these two points. This line cuts across the triangular coordinate graph, without touching the side of the triangle opposite the styrene apex which side represents varying proportions of acrylonitrile and methyl methacrylate in binary mixtures of same. Acrylonitrile and methyl methacrylate do not form a binary azeotrope. The said straight line joining the two points of binary azeotrope compositions describes three-component monomeric mixtures which, when subjected to free-radical-initiated batch polymerization, give clear terpolymers. Further, there is an appreciable area lying on each side of said line in which the terpolymers are essentially clear. However, one cannot go too tar from this line without producing terpolymers which are not clear but range from hazy to opaque materials. The invention particularly applies to the area lying within 5 percent on each side of said line; said 5 percent s measured on the graph in a direction normal to the line, and is equal to tive onehundredths of the shortest distance between an apex and the side of the triangle opposite that apex. (Another way of saying the same thing is that the invention particularly applies to the area of the graph bounded by two lines on opposite sides of and parallel to and 5 graphical units distant from said line.) Terpolymers made by polymerizing a monomeric mixture having a composition lying in the area Within 5 percent on cach side of the line joining the two binary polymerization azeotrope compositions, are generally clearer than polymers made from similar monomeric mixtures lying farther away from and on the same side of the line. In most systems all terpolymers made from monomeric mixtures having compositions in the area lying within 5 percent on each side of the line are clear. In some systems the area of clarity may not extend as far as 5 percent from the line. Those skilled in the art, having had the benefit of the present disclosure, can easily determine by simple tests of the nature described herein which monomeric mixtures give clear terpolymers in a gixen polymerization system. In all events, the compositions of monomeric mixtures giving clear terpolymers will be found to constitute an area lying along and encompassing the line joining the two binary polymerization azeotrope compositions.

The reasons for the clarity of terpolymers made as described are not known. The line joining the two binary azeotrope compositions does not represent what might be called a series of three-component azeotrcpcs. From much detailed data which we have obtained, thc relative proportions of the three monomers in terpolymers made from monomeric mixtures lying along said line are not identical to the monomeric mixture from which the terpolymer is being prepared. In other words, during the course of a batch polymerization of a monomeric mixture whose composition is taken from the line, the cotnposition of residual monomeric material drifts and the terpolymers so formed are not homogeneous mixtures ot' polymer molecules all of which contain monomer units in the same ratio, but rather are mixtures of polymer molecules having varying proportions of the three monomer units therein. No heretofore known scientific facts or theories of interpolymerization explain our discovery. However, regardless of the various reasons for believing that terpolymers made from compositions lying along the line as aforesaid would be heterogeneous, and regardless ofthe' 1actual reasons for the clarity of vsuch terpolymersi itvis'apparent'that the present invention makes possible' the production of clear terpolymers with obvious attend ant advantages, especially in films and molded articles I made vfrom the terpolymers.

The accompanying drawings are triangular coordinate graphs showing compositions ,of some three-component monomeric mixtures that giveclear terpolymers on being subjected to free-radical-initiated batch polymerization..

Figure I represents the system styrene/ acrylonitrile/diethyl fuma'rate.

Figure II represents the system trile/methyl methacrylate.

Figure III represents the system trile/methyl vinyl ketone.

Figure IV represents the system trile/methacrylonitrile.

Figure V represents the system lonitrile/methyl methacrylate.

Figure VI represents the system trile/monoethyl maleate.

Figure VII represents the system trile/normal-butyl methacrylate.

Figure VIII represents the system trile/isopropyl methacrylate.

By the present invention we can subject agiven monomeric mixture consisting of three monomers, selected as described herein, to a batch polymerization and carry the polymerization reaction to complete or essentially complete, say 90 to .100 percent, conversion of all of the monomers and yet obtain a clear solid resinous terpolymer. If desired, the polymerization can be stopped at any point short of completion so long as polymerization conditions are such as to produce solid terpolymer, but this is notnecessary in order to obtain a clear terpolymer and would seldom be advantageous. The` higher the degree of conversion of monomeric mixtures, the greater the advantages of our invention. This is because the greatest extent of heterogeneity is found with complete conversion to polymers. A high conversion, i. e.,'at least 50 weight percent conversion and preferably at least 80 weight percent conversion, is preferred in practicing the invention. However, some of the benets of the invention may be realized even where the percentage conversion is as low as 20 percent. With very low conversions, the polymer formed tends to approach the perfect homogeneity existing in the first infinitely small increment of polymer formed. s pointed out above, commercial practicality requires that conversion be carried to a value more than a few percent, hence introducing the lack of homogeneity which up to now, the art has not vknown how to avoid other than by techniques such as gradual monomer addition. It is to be recognized that the extent of the area of clear terpolymers, lying along the line joining the two binary polymerization azeotrope compositions, is dependent not only on the particular polymerization system but also on the perstyrene/ acrylonistyrene/ acrylonistyrene/ acrylonivinylxylene/acrystyrene/ acrylonistyrene/ acrylonicentage conversion, said area being the greater the lower f the percentage conversion, and the smaller the higher the percentage conversion. It is observed that the terpolymers become clearer as the composition of the monomeric mixture approaches the line joining the two binary azeotrope compositions, the general rule being that the clearest terpolymers are those derived from monomeric compositions lying on the line.

y It is usually desirable that the three-component monomeric mixture contain at least 2 weight percent, and preferably at least 5 weight percent, of the monomer present in the smallest amount.

The invention is broadly applicable to any free-radical-initiated interpolymerization of three-component monomeric mixtures containing lthe monomer combinations and in the proportions set forth herein, provided the polymerization is carried out by a batch procedure. By this it is meant that all of the monomeric materials to be proportions into the polymerization reaction system. Or`

`recovery of polymer from the last in the series.

dinarily a single charge ofmonomeric materials will be placed in a reaction vessel and the single charge sub'-` jected to polymerization conditions until the polymerization is substantially complete. However, it is not outside the scope of our invention to introduce continuously a monomeric mixture containing the three monomers in iixed proportions into a how-type polymerization system, whereby the initial polymerizable mixture passes'away from its point of introduction and ultimately is recov-r ered as polymer. This can be accomplished by continuous flowing of the monomeric mixture into the li'rst of a series of polymerization reaction' vessels with continu-` ous flow of reaction mixture from one'vessel to another along a series of two or more such vessels with ultimate Those skilled in the art will understand that this operation is essentially a batch operation in the sense that additional monomeric material of composition different from the original mixture isnot introduced into a partially poly` merized material. Thus, the term batch polymeriza-A tion, as used herein, means a polymerization which does not involve the gradual or incremental or subsequent ad@ dition of a monomer kor monomers having a composition different from the initial monomeric mixture.

This invention is perhaps most advantageously ef-` fected vby the mass or bulk polymerization procedure.V In such procedure the reaction mixture is free from added solvent or other reaction medium and consists solely of monomers, resultant polymers, and catalyst and regulator, if any. r An important advantage of the invention'is that'such a mass polymerization can be effected to produce a clear terpolymer in a situation in which it is impossible to use the gradual monomer addition technique discussed above.

Ifvdesired, the interpolymers of the present invention can be made by the suspension or the emulsion polymerization techniques. For suspension polymerization a reaction medium such as water is used together with a small amount of suspending agent, for example tricalcium phosphatecarboxymethylcellulose, etc., to give a suspension of particles of initial monomeric mixture, which particles are not of such small size as to result in a permanently stable latex. lWhere the particles are of quite large size, this type of polymerization is often called pear polymerization. To effect emulsion polymerization, suicient amount of emulsifying agent, for example a water-soluble salt of a sulfonated long chain alkyl aromatic compound, a surface active condensation product of ethylene oxide with long chain aliphatic alcohols or mercaptans, etc., is employed along with vigorous agitation whereby an emulsion of the reactants in water is formed and the product is obtained in the form of a latex. The latex can then be coagulated if desired by known methods and the polymerfseparated from the water. For some applications the latex can be employed directly as for example for forming a lilm, and the resulting lm after evaporation of the water will be clear when the polymers are made in accordance with the Apresent invention. 'The emulsion technique has certain a solvent` ordinarily results in a polymer of lower mo lecular weight than .that obtained in the absence of the.l

solvent. 'i

Conventional Vrecipes `and procedures for eecting mass, solvent, `suspension and emulsion polymerizations are :so well-known to those skilled in the art, that they need not be further detailed here. f v

From the foregoing, it will be apparent that the term, .monomeric mixture, as used in the claims refers only to the polymerizable monomeric materials used in the process, and that additionally solvents, aqueous reaction media, catalysts, etc., can be present or not in the reaction mixture as may be desired in any particular case. ln other words, in the claims monomeric mixture is notnecessarily synonymous with reaction mixture.

Polymerization can be effected by any of the wellknown free radical mechanisms. The polymerization is initiated and carried on by virtue of free radicals, which can be `derived from `the monomers themselves on simple heating of the monomeric mixture to a suitable temperature, Vor can be derived from added free-radical-supplying catalysts, especially the per compounds and the fazo compounds, or can be derived by ultra-violet or other irradiation of the reaction mixture with or without the presence of photosensitizers, e. g., organic disuldes. The examples set forth hereinafter describe thermal" polymerizations in which the polymerization reaction was initiated and maintained merely by heating the monomeric mixture in the absence of any added catalyst. ln many instances it will be desired to add a suitable polymerization catalyst, in which case suicient catalyst is employed to give a desired reaction rate. Suitable catalysts are of the free-radical-promoting type, principal among which are peroxide-type polymerization catalysts, and azo-type polymerization catalysts. Those skilled in the art are now fully familiar with a large number of peroxide-type polymerization catalysts and a suitable one can readily be chosen by simple trial. Such catalysts can be inorganic or organic, the latter having the general formula: ROOR", wherein R' is an organic radical and R is anorganic radical or hydrogen. These compounds are broadly termed peroxides, and in a more specific sense are hydroperoxides whenR is hydrogen. R and R" can be hydrocarbon radicals or organic radicals substituted with a great variety of substituents. By way of example, suitable peroxide-type catalysts include benzoyl peroxide, ditertiary butyl peroxide, tertiary butyl hydroperoxide, diacetyl peroxide, diethyl peroxycarbonate, Z-phenyl propane-Z-hydroperoxide (known also as cumene hydroperoxide) among thel organic peroxides; hydrogen peroxide, potassium persulfate, perborates and other per compounds `among the inorganic peroxides. l

The azo-type polymerization catalysts are also well-known to' those skilled in the art. These are characterized by the presence in the molecule of the group NSN- bonded to one or two organic radicals, preferably at least one of the bonds being to a tertiary carbon atom. Byway of example of suitable azo-type catalysts can be mentioned a,e-azodiisobutyronitrile, p-bromobenzenediazonium lluoborate, N-nitroso-p-bromoacetanilide, azomethane, phenyldiazonium halides, diazoaminobenzcne, p-bromobenzenediazonium hydroxide, p-tolyldiazoaminobenzene. The peroxy-type or azo-type polymerization catalyst is used in small but catalytic amounts, which are generally not in excess of one percent by weight based upon the monomeric material. A suitable quantity is often in the range of 0.05 to 0.5 percent by weight.

Photopolymerization is another suitable procedure for carrying out the present invention. This is ordinarily accomplished by irradiating the reaction mixture with ultraviolet light. Any suitable source of light is employed having effective amounts of light with wave lengths of 2,000 to 4,000 Angstrom units. The vessel in which the polymerization is conducted should be transparent to`light of the desiredwave length so that the lightcan pass through the sides` of the container. Suitable glasses are available commercially and include borovsilicate (fPyrex.), Vycor, and soft glass. Alternatively, the source of light can be placed directly over the surface of the monomer in a container or can be placed within the reaction mixture itself. In some instances it is helpful to add a material that can be termed a photosensitizer, i. e., a material which increases the rate of photopolymerization, for example organic disuliides as described in U. S. Patent No. 2,460,105.

Choice of a suitable temperature for a given polymerization will readily be made by those skilled in the art having been given the benefit of the present disclosure. In general, suitable temperatures will be found within the range of 0 C. to 200 C., although temperatures outside this range are not beyond the scope of the invention in its broadest aspects. The time required for complete polymerization will depend not only upon the temperature but also upon the catalyst if any is employed, the ability of the system to remove heat of polymerization, and the particular monomers employed. The examples set forth hereinafter give some illustrative information as to reaction times for particular polymeri` zations.

The term triangular coordinate graph as used herein is well understood. The accompanying figures are examples of such graphs and the use of same. However, for the sake of completeness the following statement can be made concerning the character of such triangular graphs. The graph is an equilateral triangle, divided oif by three series of parallel lines each series being parallel to one side of the triangle. The distance between an apex of the triangle and the side opposite that apex represents variations in percentages of the component designated by that apex varying from 100 percent to 0 percent in equal increments running from the apex to the opposite side of the triangle. For example, if the distande between the apex and the side of the triangle opposite the apex is divided into 100 equal parts by lines passing across the triangle and parallel to said side, each line represents l percent of the component for which that apex is designated. Thus, any point within the triangle represents a single three-component composition, the indicated percentages of the three cornponents totaling 100 percent.

As an aid in the choice of suitable proportions of monomers for polymerization in accordance with the invention the following data on reactivity ratios of certain monomer pairs are presented by way of example. The values given are considered the best ones represented in the literature or otherwise known (see Copolymers, by Alfrey, Bohrer and Mark, Interscience Publishers, Inc., 1952, pp. 32-43). In many instances an attempt is made to set forth an approximate order of accuracy. These latter figures, expressed as plus or minus certain values, should not however be given too much credence since such attempts to evaluate possible errors are dependent to a considerable extent on subjective` evaluation of the data. Most of the values for reactivity ratios given are for moderate temperatures, say between about room temperature (20 C.) and 100 C. Of course, the value of the reactivity ratios for a monomer pair is a function of temperature but the variation in reactivity ratios with temperature is quite small and is of little importance unless the polymerization is to be carried out at temperatures considerably removed from those mentioned. Likewise, the

reactivity ratios given are for atmospheric or autogenous pressure. Only if the polymerization pressure is to be quite considerably increased will there be an important change in the value of the reactivity ratios. It may also be pointed out that in the case of highly watersoluble monomers the reactivity ratio values may be shifted somewhat from those given, when polymerization is effected in an aqueous system. Those skilled in the art, having been given the benefit of the present disclosure, will be able to `evaluate the effect, if any, of

reaction conditions on the values given herein and determine the extent of such effect. Similarly, those skilled lin the art can determine by well-known procedures the correct reactivity ratios for monomer pairs not specifi- 4cally set forth in they following tabulation, which tabula- `tion is given by way of example of some but not all of TABLE M1 Mz r1 T:

Acrylonitrlle 0.41 5:0.08 0.03 :1:0.03 Dlethyl tumarate- 0.30 :1:0.02 0.07 :1:0.007 Dimethylfumarat 0.21 :1:0.02 0.025:1:0.015 Methaerylic acid.. 0.15 :1:0.01 0.7 :1:0.05 Methacrylonitrile 0.30 $0.10 0.16 :1:0.06 Methyl methacrylate 0.520:l:0.02 0.460i0.026 Methyl vinyl ketone 0.29 :1:0.04 0.35 :1:0.02 Monoethy1fumarate- 0.18 :1:0.10 0.25 0.10 Monoethyl maleate..- 0.13 i0. 01 0. 03510.01

Where M1 is to be vinyltoluene or vinylxylene, the same reactivity ratios are used, on the assumption that the reactivity ratios for such systems do not differ essentially for the purposes of this invention from the reactivity ratios of the corresponding systems wherein styrene is M1. This assumes that the introduction of one or two methyl groups into the aromatic nucleus of styrene does not greatly alter the polarity and steric properties of the vinyl double bond. Likewise, when an alkyl methacrylate other than methyl methacrylate is to be used, the reactivity ratios are assumed not to diler essentially for the purposes of this invention from the above reactivity ratios involving methyl methacrylate. This assumes that a moderate increase in the chain length of the alkyl group in the alkyl methacrylates over the single carbon atom in the methyl group of methyl methacrylate, or a branching of the chain if such is present, does not greatly alter the polarity and steric properties of the vinyl double bond. Similar assumptions are made with respect to the various dialkyl fumarates as a group, with respect to the various monoalkyl fumarates as a group, and with respect to the various monoalkyl maleates as a group. Thus, although the reactivity ratios for styrene/dimethyl fumarate and for styrene/diethyl fumarate appear to differ considerably from each other, the values of the binary azeotrope compositions for these two systems calculated from said dilerent reactivity ratios, given in the table above, differ from each other by only two percentage points. Anyone skilled in the art, desiring greater precision,can use well-known standard procedures to determine the reactivityratios lfor a 1 trope compositions are easily converted to lweightpercent by use of the molecular Weights .of the particular M1 and M2. In the case of dialkyl fumarates, `alkyl`4 methacrylates, monoalkyl fumarates, and monoalkyl maleates, any of which can be copolymerized with acry-` lonitrile andA any one of the monomers styrene, vinyl` toluene, and vinylxylene in the practice of this .invenl tion, special preference is givento the lower alkyl groups.m Alkyl groups containing from 1 to 4 carbon` 10 atoms are particularly valuable, viz., -methyl,"e`thyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, ltert.- butyl. However, the invention is also applicable to the alkyl compounds mentioned, thatv contain alkyl groups of up to 8 carbon atoms per alkyl group and even higher. In the case of dialkyl fumarates, there are included'those dialkyl fumarates wherein both alkyl groups are the same and those dialkyl fumarates wherein two dilerent alkyl groups are present inthe molecule.

The followingexamples illustrate some methods for practicing the present invention with respect to certain ternary mixtures of monomers. The general applicability of the invention, and advantages thereof, are shown in these` examples. tions can be made in the particular choice of monomers, proportions, and methods of polymerization in accordance with the general teachings of the present specification, and the examples are not to be taken as coextensive with the invention in its broadest aspects.

Example This example concerns the ternary system styrene/ acrylonitn'le/diethyl fumarate. Theldata obtained inA this example are set forth graphically in Figure I of the drawings. f r.

The composition of the styrene/diethyl fumarate binary azeotrope was calculated in the following manner according to the article by Mayo and Walling, Chemical Reviews, 46, 199 (1950). The value of 0.08 used for r2 is the average of two values given in that article.

Styrene M1) Diethyl fumarate M2) [M2] 43.4 mole percent diethyl fuma'rate [M1]= 56. 6 mole percent styrene Molecular Weight of diethyl fumarate 172.2 Molecular Weight of styrene 104.1

0.434X172.2= 74.8 grams diethyl fumarate 0.566X 104.1= 58.8 grams styrene 133.6 grams mixture (74.8 X 100 133.6 56 Weight percent dieth yl f umarate (58.8 X 100)/133.6 =44 Weight percent styrene The foregoing calculations give the compositions of the styrene/diethyl fumarate binary polymerizationazeo trope as 44 weight percent styrene, 56 weight percent diethyl fumarate.` v

vBy the same procedure, the, binary polymerization azeotrope forV styrene/acrylonitrileI was calculated to be 77 weight percent styrene, 23 weight percent acrylonitrile, using slightly different reactivity ratio'values than in the examples following.

A series of monomeric mixtures was made up, each mixture being prepared by admixture of the individual pure monomers in a Pyrex test tube 150 mm.k long and having an internal diameter within the approximate range of 14 to 18 mm., usually about 16 mm. Each test tube containing the particular monomeric mixture was llushed with nitrogen in order to remove any air present in the gas space above the liquid, and the test tube was then sealed ol at the top by heating the tube under nitrogen and pulling it out in the flame to seal the tube completely. Each particular monomer mixture was prepared and polymerized in'duplicate. p .l

After the various tubes containing" the monomericniix` tures had-'been prepared,'-thcy were placed in a 90C.

It will vbe appreciated that varial .Constant-temperature bath, and heldthere for 24 hours.

`removed and placedin an oven maintained at 180 C.,

and held thereinfor 8 hours.

The various monomeric compositions are set forth in detail in `Table I. Table I designates each ditferent mix` ture by samplelnumber.` Sample No. l is the binary styrene/acrylonitrile azeotrope composition. Sample No. 6 is the binary styrene/diethyl fumarate azeotrope composition. Samples 2, 3, 4, and have compositions which fall on a straight line connecting the two binary azeotrope compositions, designated samples Nos. 1 and 6, when ploted on triangular coordinates. See Figure I.

`Samples 7 to 20, inclusive, were prepared with compositions which variedso that several series of two or Athree different compositions running along constant diethyl fumarate composition lines and cutting across the line joining the two binary azeotropes could be examined.

obtained by breaking and removing the glass tube; this cylinder of polymer conformed to the internal shape `and showed a sparkling appearance as found in high quality crystal glassware.

Several of the polymer products were analyzed for nitrogen fand the acrylonitrile content of the polymer calculated. In each instance it was close to the acrylo nitrile content of the monomeric mixture, but consistently ran slightly low, which the literature states is the uniform experience in nitrogen determinations on polymers.

The alcohol solubles content of many of the polymers was determined, using the following standard procedure:

A 0.3 gram-sample of polymer is dissolved in ml. acetone (or other suitable solvent), then the polymer is precipitated by adding 250 ml. absolute ethanol to the solution; the precipitate is coagulated, filtered off, dried and weighed. The average of two determinations is given. The alcohol solubles content (ASC) gives an approximate measure of the extent of conversion. The material soluble in alcohol is principally monomer; only very low molecular weight polymers, e. g., dimers and trimers, are soluble in alcohol. Thus, l00ASC approximates the percentage conversion.

The specic viscosity was determined on the total polymer, and on the undissolved residue from the alcohol solubles test. The specific viscosity determinations were made on a 0.1 weight percent solution of polymer in dimethylformamide.

TABLE I STYRENE/ACRYLONIIRILE/DIETHYL FUMARAILJ TERPOLYMERS Appfllee Speclile Composition, Percent Alcohol viscoslty Sample weight AN* solubles No. percent, 111 polcontent,

DEF/ANIS ymcr weight Total Insol Clarity Color 1versent: polym. uble alcohol residue oiorless DEF=dlethyl tumarate; AN=acrylonltrile; S=styrene; Sl.=sltghtly; V. sl.=very slightly. *=calculat.ed from nitrogen analysis.

CfClear: essentially crystal clear H-Hazy: some cloudiness but slight T.-Turbid: moderately cloudyv O-.-Opaque: densel cloudiness, similar to milk glass in appearance Clear means relatively free from gross amounts of haze but allows the presence of slight haze to be detected with` close examination in strong light. Specific notation that a sample was crystal clear means not only that no haze `was apparent `to the observer, but also that Athe sample lReferring now to Fig. I of the drawings, the clarity data given in Table I have been designated alongside each of the corresponding` ternary monomeric mixture composition indicated by a point on a triangular coordinate plot.. The various numerals on Fig. I located adjacent the respective points refer to the sample number in Table I. AllofA the points marked C were rated as clear, and of these `all were crystal clear with the exception of points 11 and 12, each of which had a slight haze but not suicient to consider them other than essentially clear or to bring them from the clear rating into the hazy rating.

Examination of Fig. I immediately shows that terpolymers prepared from monomeric mixtures having compositions lying on the line joining the two binary azeotrope compositions were clear, as were terpolymcrs within the area lying -along said line. However, going appreciably beyond 5` percent on each side of the line the terpolymers become Anon-clear. Thus, points 7 and 10 were hazy and point :9 was opaque. It is interesting to note that points 7 and 10' below the line are about 10 percent away from the "line and yet onlylhazy, whereas point 9 above the line is about 7 percent away from the line and yet is v ples vl2 and opaque. Such behavior is consistent with most physical phenomena which seldom exhibit perfect regularity. The data in the present example demonstrate that terpolymers made from tern-ary monomeric mixtures whose composition is taken from along the line and from a significant area lying on each side of the line are clear, .andv also that polymers falling within the area within 5 percent of each side of thevline constitute a new group of terpolymers havingl the extremely important property of clarity.

Another interesting thing to note is that by the practice of the present invention terpolymers of minimum color ordinarily result. Thus, polymers 7 and 10 of those tested,` farthest awayA from the linewere yellow, while the colorf'decrcased as the line was approached. All those polymers lying below the line had at least a trace of yellow .color but; the colorintensity decreased as the line'was approached. Those above the line had no color, other than point 9 which was white and opaque.

In Fig.-I the dashed lines drawn parallel to Athe line joining the twoy binary azeotrope compositionsv `are 5 percent on each lside ofthe line, i. e., each is a distance from the line equal to 5 percentage points of composition as determined by dividing the distance between an apex and the center-of the opposite side ofthe triangle into 100 equal equidistance parts; ingotherwords, the two dashed linesKA are on opposite sides of and 5 graphical units distant from said line. I f l vExample 2 This example presents data on the ternary system styrene/ acrylonitrile/methyl methacrylate.

Considering styrene as M1 and methyl methacrylate as M2,the reactivity ratios are r1=0.52 and r2=0.46. From these data,` in the manner set forth in Example 14,

the binary polymerization azeotrope composition Vof styrene/methyl methacrylate was calculated to be y54 weightpercent styrene and 46 weight percent methyl methacrylate.A The composition for the styrene/acrylonitrile binary polymerization azeotrope composition-was calculated to be 2 4 weight percent acrylonit'rile, 7 6 weight percentlstyrene. fl Y' e g' f Samples 'containing varying proportions of the monomers were prepared and polymerized and observations made on the polymersin .the manner 'described' in Example 1. The datafare listed in Table IIand plottedin Fig. II of the' drawings. Samples 1-14 were run `1irst.y Samples l5, 16 and 17 and -a repeat onV sample 13 were' run latenand withV a different -batchof monomers, 4which explains thefactthatisomewhat lighter yellow colors were obtainedthan wouldbe expected from the colors of sam- TABLE 1I STYRENE/ACRYLONITRILlMETHYL METHACRYLATE TERPO YMERS Compo Appearance Weight Specic Sample sltion, percent; viscosity, No. weight alcohol total percent, Clarity Color solubles polymer MMA/S/AN content 3.41 0.199 3. 71, 0.178 4.12 0.153 4.93 0.137 5.06 0.136 2.86 0.103 3.92. f 0.158 3.66 0.122 k2. 70 0.101 2. 94 0.102 V. l. yellow 2. 56 0.202

(sl. yellow). 10/65/25' L. yellow..- 4. 80 0.202 `25/55/20 Yellow Y 6.03 r0. 177 /55/10 Colorless 5.18 0.141 25/55/20 Sl. yellow--. '17/59/24 dn .do

414217 do L. yellow-" 35/37/28 OOpaqueo MMA=methyl methacrylate;y Svj=styrene; `AN=acrylonitmlle.

The data of` Table II, particularly. as. plotted on Fig. II, again" showthe Aclarity Vof .terpolymers prepared from monomeric mixtures, whosecovmposition is taken from yther line joining the two binary poymerization azeot'rope compositions. Further, polymers made from compositions taken at a considerablepdistance on each side of the line are likewise clear. yAs in Example 1 with the styren/acrylonitrile/diethyl fumarate terpolymers, opacity increases more quickly above the line as higher concentrations of styrene are approached than itdoes below the line. Thus, in the present system styrene/acrylonitrile/methyl methacrylate, point 7, which isy essentially on the 5 percent line, is opaque,so that the area lof perfectly clear terpolymers along the line does not extend quite to the S percent line at this point of the graph: However, point10, which is .about 4 percent away'from the line in the same direction as point 7, is clear. Below theA line, points 11, 12, 13, 14,15 and 16 are clear, and of these points 12, 13, 15 and 16 are well beyond the 5 percent distance-from the line. However, with those points it will be noted that thek color was yellow'anrl hence polymers not farther than 5 percent away from the line are preferred.` Point 17 is in the opaque area.

The viscosity data in Table II show the eifect of composition on viscosity. Thus-increase in concentrationxof either styrene or methyl methacrylate decreases the molecular weight. By virtue of the present invention, one can choose a terpolymer composition within a considerable range of molecular weights and yet having clarity.

Example 3 vinyl ketone was calculated, taking styrene as M1 and methyl vinyl ketone as M2. The reactivity ratios used were r1=0.29 and r2=0.35. The binary polymerization azeotrope composition was determined to be 42 weight percent methyl vinyl ketone, 5 8 weight percent styrene.

The binary polymerization azeotrope composition for styrene/acrylonitrile was taken as 76 weight percent styrene, 24 weight percent acrylonitrile.

Samples containing varying proportions .of the monomers were prepared and p'olymerized and observations made on the polymers in the manner described in Example l. However, the polymerization cycle was 29 hours at C., 20 hours at 120 C., and finally 8 hours at C. The'- data are listed in Table III and plotted in Fig. III of the drawings.

TABLE III S =styrene;" AN=aorylonltrile; MVK=methyl vinyl ketone.

As in the other examples, the terpolymers prepared 15 r and opaque and white. Points 7, 8 and 9, which are on the opposite side of the line and more than percent away from the line, were all yellow, points 7 and 8 being hazy and point 9 turbid. r

Example 4 This example presents data on the ternary system styrene/ acrylonitrile/ methacrylonitrile.

Considering styrene as M1 and methacrylonitrile as M2, the reactivity ratios are r1=0.30 and r2=0.l6. From these data, in the manner set forth in Example l, the binary polymerization azeotrope composition of styrene/ methacrylonitrile was calculated to be 65 weight percent styrene, 35 weight percent methacrylonitrile. The cornposition for the styrene/acrylonitrile binary polymerization azeotrope composition was taken at 24 weight percent acrylonitrile, 76 weight percent styrene.

Samples were prepared and tested in the manner set forth in Example 1. For samples Nos. 1 to 10, inclusive, the polymerization cycle was 24 hours at 90 C., 24 hours at 120 C., and 8 hours at 180 C. For samples Nos. 1l to 20, inclusive, the polymerization Acycle was 24 hours at 90 C., 30 hours at 120 C., and 8 hours at 180 C. This difference was a matter of convenience and did not significantly aiect the observed polymer properties.

The iirst eight compositions selected for test fall on the line joining the two binary polymerization azeotrope compositions. Samples 9-12, inclusive, intercept that line at l0 percent methacrylonitrile concentration. Samples no 13-17, inclusive, intercept the line at Y5 percent acrylonitrile composition. Samples 18, 19 and 20 intercept the line at about equal weight percentages of acrylonitrile and methacrylonitrile with decreasing percentages of styrene. The data on compositions and polymer properties are set forth in Table IV.

Sustyrenc; AN=acrylonltrlle; MNf-methacrylonitrile.

The data of Table IV on composition of monomeric mixtures and appearance of polymers are set forth graphically in Fig. IV of the drawings. It will be noted that all of the polymers made from terpolymer compositions lying within 5 percent of each side of the line joining the two binary polymerization azeotrope compositions were clear with the exception of point 18. This point, lying 4 percent away from the line in the direction of increasing styrene concentration, contained a white haze and therefore is not considered to be within the area of clear terpolymers lying along the line. However, even here it is interesting to note that the haziness appears only at a considerable distance from the line; note clear points 11 and 15. Polymers within 3 percent of the line on this side of the line are clear.1 As in the other examples, opacity appears more quickly as one moves away from the line in the direction of increasing styrene concentration than it appears moving away from the line in the opposite direction. However, point 9 below the line and outside the 5 percent distance was hazy and point 20 similarly located but having a greater quantity of methacrylonitrile and being somewhat4 farther from the line was turbid.

With respect to color, the observation made earlier that the practice of the present invention permits the production of polymers having minimum color is also borne out in this example. Color in general increases as one moves away from the line. However, with this system it appears that increasing color is somewhat related to increasing methacrylonitrile content and decreasing acrylonitrile content with a given styrene content, and the color also increases inthe direction of decreasing styrene content.

Example 5 This example presents data on the ternary system vinylxylene/acrylonitrile/methyl methacrylate.

The reactivity ratios for the system vinylxylene/acrylonitrile, and for the system vinylxylene/methyl methacrylate, were assumed not to differ `essentially for the purposes of this invention from the reactivity ratios of the corresponding systems styrene/acrylonitrile and styrene/ methyl methacrylate, respectively. This assumes that the introduction of two methyl groups into the aromatic nucleus of styrene does not greatly alter the polarity and steric properties of the vinyl double bond. Mole ratios for the two binary polymerization `azeotropes were calculated in the manner described in the preceding examples, and these were then converted to weight ratios, employing the molecular weight of vinylxylene in each instance instead of the molecular weight of styrene.

In this manner the binary polymerization azetrope composition of vinylxylene/acrylonitrile was calculated to be 80.3 weight percent vinylxylene, 19.7 weight percent acrylonitrile. Similarly, the binary polymerization azeotropc composition of vinylxylene/ methyl methacrylate was calculated to be 59.7 weight percent vinylxylene, 40.3 weight percent methyl methacrylate.

Samples were prepared and tested in the manner set forth in Example l. The vinylxylene employed was a mixture of isomers, and was believed to contain a small amount of close-boiling saturated alkylbenzenes. This impurity, of course, could be expected to affect the polymerization results to some extent.

Samples 1 to 6, inclusive, fall on or approximately on the line joining the two binary polymerization azetrope compositions. Samples 7 and 8 were selected to lie fairly close to the line and on opposite sides of the line. Samples 9 and l0 lie the greatest distance from the line in the direction of increasing vinylxylene content, whereas samples 15-18 are on the opposite side of the line and cover a variety of compositions. Samples 1l and 12 are binary mixtures of vinylxylene with methyl methaerylate,`

and samples 13 and 14 are binary mixtures of vinylxylene with acrylonitrile. The data on compositions and polymer properties are set forth in Table V, and shown graphically in Fig. V of the drawings.

1 If the value of the binary styrene/methacrylonitrlle azeotrope compositlon 1s calculated from r1=0.25 and r2=0.25, which reactivlty ratios for this binary system have been reported in the literature, the azeotrope is 61 percent styrene, 39 percent methacrylonitrile. Using this (rather than 65 percent styrene, 35 percent methacrylonitrile used in drawing .Figa lV), hazy point 18 falls just outside the 5 percent line, 1. e. 1s sllghtly more than 5 percent away from the line joining the. two bmary azeotropes. It is possible these reactivity ratios are more accurate. However, the ratios r1=0.30 and r2=0.16 are considered probably better and have therefore been used 1n the calculatwns made for this example.

TABLEV. TABLE VI VIN YLXYLENE/AORYLONITRILE/METHYL METHAC- STYRENE/AORYLONITRILE/MONOETHYL MALEATE TER p RYLATE TERPOLYMERS y .POLYMERS Composition, Appearance 5 Composition, Appearance Saple Xigiiilc/ii Sliipe Vlghtt reen o l Clarity Color S/AN/MEM Clarity Color /40/ C-Olear (sparkling) Colorless. 76/24/ 0 C-C1ear Colorless. 3/34/63 do Do. 73/21/ 6 d Lt. yellow. 6/28/66 C-Clear (sl. haze). Bluish white. 65/15/20 Do, 1l/18/71 -do D0. 57/ 9/34 D0.

7/77 C-C1ear(v. sl. haze) Colorless 45/ 0/55 Colorless 20/ 0/80 C-Clear Sl. yellow 68/12/20 White. 10/23/67 C-Clear (sparkling). Colorless. /23/ Lt. yellow 12/12/76 -Hazy Bluish white 62/18/20 D0, hite. 58/22/20 Do.

Do. 50/30/20 Yellow. Colorless. /60/20 Lt. yellow (soit and,

Do. sticky). Sl. yellow. 75/ 5/20 White.' White. 80/10/10 Do. Bluish white. L. yellow. Yellow. 20 S=styrene; AN=acrylonitrile;'MEM==monoethyl maleate; Sl. allow. y As 1n the other examples, 1t will be observed that the' It will be noted in examining the drawing .and data that A all of the ploymers made from monomer mixtures whose compositions 'lie on the line joining the two binary polymerization azeotropes were clear.- Some slight variations in appearance are noted, but none of these samples departs atall from the clear category.` Similar to the eriect'noted in the preceding examples, clarity decreases muc'h more rapidly in the direction lof increasing vinylxylene concentrationY than in theopposite direction when` moving away fromthe line. Thus, point 7 was of sparkling clarity, while point 8 on the opposite side of the line and'containing a larger quantity of vinylxylene wask Example 6 This examplevpresents data on the ternary system styrene/ acrylonitrile/ monoethyl maleate. f

Considering; styrene as Mland monoethyl maleate as M3, the reactivity ratios are r1=0.13 and r2=0.035. From these'data,.in` the manner set forth in Example 1, the binary polymerization azeotrope composition of styrene/ monoethyl maleate was calculated to be 44.7 weight percent styrene, 55.3 weight percent monoethyl maleate. The composition for the styrene/ acrylonitrile binary polymerization azeotrope composition was similarly calculated as 76.3 weight percent styrene, 23.7 weight percent acrylonitrile.

Samples were prepared' 'and` tested in the manner set forth 'inEXample 1. For mos't of the samples the polymerizaton cycle was 24 hours at 90 C., 25 hours'at 120 C., and 71/2 hours at 180 C. For samplesv 5 and 9 the cycle was 24 h ours at 90 C., 461/2 hours at 120 C. For sample 11,]the cycle was 24 hours at 90 C., 25v hours at 120 C.

The first Iiive compositions selected for test fall on the line joining the two binary polymerization azeotrope compositions. n Samples 6, 8, 9, 10, 11 and 12, as well as sample 3, cut across that line on a line of constant 20 weight percent monoethyl maleate, thus covering a wide variety of compositions. Samples ,7 and A113 areon opposite sides of the line from each other, are disposed at 4a'considerable distance from the other points, and contain 10 percent and less-monoethyl maleate.

The `data onA compositions and polymer properties are set forthvin Table VI, and Vare. givenxgraphically in Fig. VI of the drawings.

1 ltion azeotropes are clear.

polymers made from monomeric mixtures whosecompo- I sitions fall on the line joining the two binary' polymeriza'- f Further, the area of clarity 'i lying alongthe line is appreciable, and is greater 4below the line, i. e., in the direction of decreasinglstyrene con-' tent, than abov'e'the line' in the direction of increasing styrene' content. Thus, point lying between 3 and 4j percent away from the line in thedirection of increasing',V

styrene content, was opaque, so that the area of clear terpolymers doesnot extend this far in this'part of the graph. ln comparisonpoint, directly opposite point 6 on the other side of the line, `is, clea'rgs'ee also point l7.

Continuing along the20 percent monoethylrnaleateline" point 9, which is about -8` percent away from theline, rs1. clear. Hoy/ever, by thetime point 10 'is rea'cliedf'the`ly polymer made frornthe monomeric having that composi- .f

tion is' turbid, and`stillffu1ther away from the Aline point 1l whose polymer'was opaque. 'On the oppositeside of the line, points 12. and 13 are opaque.

rlhese data show that, as in other examples, opacity'i appears more quickly as one 'moves away fromv the'line in the direction ,ofjincreasing styrene concentration that it appears in moving away from the line in' the opposite direction.

The dished linesdrawn on each side of the line and 5 percent away from that lineincludes co'mp osi ,y

tions which are preferred. Even in those regions of the composition diagram in' which non-clear polymers are formed,`e. g. point 6, such polymers are more transparent,

i. e. less opaque, than those" drawn from compositions" in the `same region but lying'k outside the 5 percent line, e. gypoint 12.' K f Example 7 yThis example presents data on the .ternary system styrene/acrylonitrile/normal butyl methacrylate.

The reactivity ratios for"thebinary system? styrene/nbutylrnethacrylate were assumed not A`to differ essentially for the purposes`pfithis invention from'the reactivity ratios of the corresponding system styrene/methyl methacrylate. This assumes that a moderate increase in the chain llength of the alkyl group in the alkyl methacrylates over the single carbon atom .in the methylgroups of methyl methacrylate does not greatly alter the polarity andsteric propertiesA of the vinyl double bond.v Mole I rati-os for the binary polymerization' azeotrope were calculated in the manner described'in Example l, and these were then converted toweight ratios, 'employing therk l molecular weightofmbutyl'methacrylate instead of the y molecular weight vofmethyl methacrylate. V

In this lmanner the binary polymerization azeoltrop'e composition ofstyrenc/n-'butyl methacrylate was calcul latedto be 472 weight percentstyrene, 52.8 weight percent nibutyl-methacrylate'.' Similarly," the binary poly- `,merization azeotrope composition of styrene/acrylonitiil 19 was calculated to be 76.3 weight percent styrene, 23.7 weight percent acrylonitrile.

Samples were prepared and tested in the manner set forth in Example l. The polymerization cycle was 24 hours at 90 C., 24 hours at 120 C., 8 hours at 180 C. A variety of ternary compositions was chosen to cover points on or approximately on the line joining the two binary azeotrope compositions and a considerable number of points on either side of that line. The data on compositions and polymer properties are set forth in Table VII, and shown graphically in Fig. VII of the drawings.

TABLE VII f Com tten Appearance Do: Colorless.

ellow.

S-stymne; AN==ncrylonitrlle`n-BMAznormal butyl mcthacrylate These data again show that terpolymers prepared from monomeric mixtures whose compositions are taken from along the lin'e joining the two binary polymerization azeotrope's fareclear and that the area of clarity is not restricted to the linebut coversa significant area along the line.

Points 11 and 14 further demonstratethat, the area of clarity in this portion of the graph extends a very considerable distance away from the line. Howeven points 7, 9, and 10 lying in the neighborhood of 3 percent away from `the line point out regions wherein the area of perfect clarity does not extend very far from the line. Even in' these regions, however, polymers within 5 percent of the line on either `side are preferred as they are clearer and less opaque thansimilar polymers farther away from the line.` 'I`hus,tforv example, `compare points 9 and 8 and points 7 and 15. f

t Exaimple 8 Thisexample presentsI data on the ternary system styrene/acrylonitrile/isopropylv methacrylate.

The reactivity ratios for the binary system styrene/isopropyl methacrylate were assumed not to differ essentially forthe purposes of this` invention from `the reactivity ratios `for `the corresponding systems styrene/ methyl methacrylate (Example 2) and styrene/n-butyl methacrylate (Example 7). The results obtained proved this assumption to bev correct, and that a change in chain length ofthe alkyl group from one,pr four to three carbon atoms, or a branching of the'cha'in in the alkyl group asA compared with the straight chain alkyl group o instead Lof the molecularweight of methyl methacrylate.

In `this manner the binary polymerization azeotrope composition of styrene/isopropyl `methacrylate was calculated to be 47.7, weight percent styrene, 52.3 weight percent` isopropyl methacrylate. Similarly, the binary polymerization azeotrope z composition off styreneacrylofteA 2Q nitrile was calculated to be 76 weight percent styrene, 24 weight percent acrylonitrley Samples were prepared and tested, and observations made, as set forth in Example l. The polymerization cycle was 24 hours at 90 C., 24 hours at 120 C., 8 hours at 180 C. A variety of ternary compositions was chosen to cover points on the line joining the two binary azeotrope compositions :1nd a considerable number of points on either side of that line. The data on compositions and polymer properties are set forth in Table Vlil, and shown graphically in Fig. VIII of the drawings.

TABLE VIII STYRENE/ACRYLONITRILE/ISOPROPYL It/IETHACRYLAT E TERPOLYMERS Sample N o.

C-S arkling clear-: Do

S =styrene; AN=acrylon1trlle; l-PMA=isopropyl methacrylate.

These data again show that clear terpolymers prepared from monomeric mixtures whose compositions are taken from along the line joining the two binary polymerization azeotropes are clear, and that the area of clarity is not restricted to the line but covers a significant area along theline. As noted in `previous examples, the clarity decreases more rapidly as compositions are chosen moving away from the line in the direction of increasing styrene content, than in compositions moving away from the line on the opposite side of the line.` Compare, for example, points 7 and 8, each about 4 percent away from the line on the side of increasing styrene content and each of which is hazy, with` point 9 about 4 percent away from the line on the opposite side of the line and which is clear. In the case of points 7 and 8 and adjacent compositions, polymers within 5 percent of the line are preferred as they are clearer and less opaque than similar polymers farther away from the line; compare, `for example, points 7 and 12, the former being only hazy and the latter turbid. It is also noted that point 11 demonstrates that the area of clear terpolymers extends for a much greater distance away from the line in that region than on the opposite side of the line. It is interesting to note even here, however, that though point 4 was light yellow and points 5 and 6 were colorless, point 11 is yellow and thus not as preferred as the points nearer the line or on the line.

As in the other examples, the dashed lines drawn on each side ofthe principal line and 5 percent away from that line includes compositions which are preferred.

While the invention has been described herein with particular reference to various preferred embodiments thereof, and examples have been given of suitable proportions and conditions, it will be appreciated that variations from the details given herein can be effected without departing from the invention. When desired, the terpolymers of the present invention can be blended with other polymers, plasticizers, solvents, fillers, pigments, dyes, stabilizers, and the like, in accordance with the particular use intended.

We claim:

il. A clear terpolymer prepared by free-radical-initiated batch polymerization to a conversion of at least 20 weight percent of a monomeric mixture consisting of (a) a monomer selected from the group consisting of styrene,

salaires vinyltoluene and vinylxylene,' (b)L acrylonitrile, and (c) a dalkylfumarate, the proportions of the three monomers in said monomeric mixture being limited to those in the area of mixtures that-produce clear terpolymers, said area encompassing the line joining the polymerization azeotrope composition of the particular (a) and acrylonitrile on the one hand and the particular (a) and said dialkyl fumarate on the other hand as plotted on an equilateral triangular coordinate graph.`

2. A clear terpolymer prepared by free-radical initiated batch mass polymerizationV to a conversion of 'at least 20 weight percent of a monomeric mixture consisting of (a) a monomer selected from the group consisting of styrene, vinyltoluene 'and vinylxylene, (b) acrylonitrile, and (c) a dialkyl fumarate, the proportions of the three monomers in said monomeric mixture being limited to those in the area of mixtures that produce clear terpoly mers, said area encompassing the line joining the polymerization azeotrope composition of the particular (a) and acrylonitrile on the one hand the particular (a) and said dialkyl fumarate on the other hand as plotted on an equilateral triangular coordinate graph.

3. A clear terpolymer prepared by free-radical initiated batch mass polymerization to a conversion of at least 20 weight percent of a monomeric mixture consisting of (a) styrene, (b) acrylonitrile, and (c) a dialkyl fumarate, the proportions of the three monomers in said monomeric mixture being limited to those in the area of mixtures that produce clear terpolymers, said area encompassing the line joining the polymerization azeotrope composition of styrene and acrylonitrile on the one hand and styrene and said dialkyl fumarate on the other hand as plotted on an equilateral triangular coordinate graph.

4. A clear terpolymer prepared by free-radical initiated batch polymerization, in an aqueous medium, to a conversion of at least 20 weight percent, of .a monomeric mixture consisting of (a) a monomer selected from the group consisting of styrene, vinyltoluene and vinylxylene, (b) acrylonitrile, and (c) a dialkyl fumarate, the proportions of the three monomers in said monomeric mixture being limited to those in the area of mixtures that produce clear terpolymers, said area encompassing the line joining the polymerization azeotrope composition of the particular (a) and acrylonitrile on the one hand and the particular (a) and said dialkyl fumarate on the other hand as plotted on an equilateral triangular coordinate graph. Y

5. A clear terpolymer prepared by free-radical initiated batch polymerization to a conversion of at least 20 Weight percent of a monomeric mixture consisting of (a) styrene, (b) acrylonitrile, and (c) a dialkyl fumarate,

the proportions of the three monomers in said monomeric l mixture being limited to those in the area of mixtures that produce clear terpolymers, said area encompassing the line joining the polymerization azeotrope composition of styrene and acrylonitrile on the one hand and styrene and said dialkyl fumarate on the other hand as plotted on an equilateral triangular coordinate graph.

6. A clear terpolymer prepared by free-radical initiated batch polymerization to a conversion of at least 20 weight percent of a monomeric mixture consisting of (a) styrene, (b) acrylonitrile and (c) diethyl fumarate, the proportions of the three monomers in said monomeric mixture being limited to those in the area of mixtures that produce clear terpolymers, said area encompassing the line joining the polymerization azeotrope composition of styrene and acrylonitrile on the one hand and styrene rand diethyl fumarate on the other hand as plotted on an equilateral triangular coordinate graph.

7. A polymerization process which comprises forming a 3-component monomeric mixture consisting of (a) a monomer selected from the group consisting of styrene, vinyltoluene and vinylxylene, (b) acrylonitrile, and (c) a dialkyl fumarate, the proportions of the three monomers in said monomeric mixture being limited to those in the area of mixtures that produce clear terpolymers, said area encompassing the line joining the polymerization azeotrope composition of the particular (a) and acrylonitrile on the one hand andthe particular (a) and said dialkyl fumarate on the other hand as plotted on an equilateral triangular coordinate graph, and subjecting a batch of said monomeric mixture to free-radical initiated batch polymerization forming an essentially clear, homogeneous, high molecular weight terpolymer in an amount of at least 20 weight percent of said monomeric mixture. y 8. A ypolymerization process which comprises vforming a 3-component monomeric mixture consisting of (a) a monomer selected from the f group consisting of styrene, vinyltoluene and vinylxylene, (b) acrylonitrile, and (c) a dialkyl fumarate, the proportions of three monomers in said `monomeric mixture being limited to those in the area ofl mixtures that produce clear terpolymers, said area encompassing the line joining the polymerization azeotrope composition of the particular (a) and acrylonitrile on the one hand and the particular (a) and said dialkyl fumarate on the other hand as plotted on an equilateral triangular coordinate graph, and subjecting a batch of said monomeric mixture to free-radical initiated batch mass polymerization forming an essentially clear homogeneous high molecular weight terpolymer in an amount of at least 2O weight percent of said monomeric mixture.

9. A polymerization process which comprises forming a 3-component monomeric mixture consisting of (a) styrene, (b) acrylonitrile, and (c) a dialkyl fumarate, the proportions of the threemonomers in said monomeric mixture being limited to those in the area of mixtures that produce clear terpolymers, said area encompassing the line joining the polymerization azeotrope composition of styrene and acrylonitrile on the one hand and styrene and said dialkyl fumarate on the other hand as plotted on an equilateral triangular coordinate graph, and subjecting a batch of said monomeric mixture to free-radical initiated batch mass high conversion polymerization forming an essentially c'lear homogeneous high molecular weight terpolymer.

10. A process according to claim 7 wherein said monomeric mixture consists of (a) styrene, (b) acrylonitrile and (c) a dialkyl fumarate.

l1. A process according to claim 7 wherein said monomeric mixture consists of (a) styrene, (b) arcrylonitrile and (c) diethyl fumarate.

12. A clear terpolymer prepared by free-radical-initiated batch polymerization to a conversion of at least 20 weight percent of a monomeric mixture consisting of (a) a monomer selected from the group consisting of styrene, vinyltoluene and vinylxylene, (b) acrylonitrile, and (c) a dialkyl fumarate, the proportions of the three monomers in said monomeric mixture being limited to those in the areak of mixtures that produce clear terpolymers, said area encompassing the line joining the polymerization azeotrope composition of the particular (a) and acrylonitrile on the one hand and the particular (a) and said dialkyl fumarate on the other hand as plotted on an equilateral triangular coordinate graph, with the further limitation that said proportions of the three monomers are restricted to the area of said graph bounded by two lines on opposite sides of and parallel to and 5 graphical -units distant from said line.

13. A clear terpolymer prepared by free-radical-initiated batch polymerization to a conversion of at least 20 weight percent of a monomeric mixture consisting of (a) a monomer selected from the group. consisting of styrene, vinyltoluene and vinyxylene, (b) arcylonitrile, and (c) a dialkyl fumarate, the proportions of the three monomers in said monomeric mixture being designated by the line joining the polymerization azeotrope composition of the particular (a) and acrylonitrile on the one hand and the particular (a) and said dialkyl fumarate, on the other hand as plotted on an equilateral triangular coordinate graph.

14. A clear terpolymer prepared by free-radical-initiated batch polymerization to a conversion of atleast 20 weight percent of a monomeric mixture consisting of (a) styrene, (b)`acrylonitrile,and (c) diethyl fumar-ate, the proportions of the three monomers in said monomeric mixture being limited tothose` in the area of mixtures that produce clear terpolymers, said area encompassing the line joining the polymerization azeotrope composition of styrene and acrylonitrilc on the one hand and styreneing of (a) styrene, (b) acrylonitrile, and (c) diethyl fumarate, the: proportions of the three monomers in said monomeric mixture being designated by the line joining the polymerization azeotrope composition of styrene and acrylonitrile on the one hand and styrene and diethyl fumarate on the other hand as plotted on an equilateral triangular coordinategraph.

References Cited in the file of this patent UNITED STATES PATENTS 2,417,293 DAlelio Mar. 11, 1947 2,426,728 DAlelio Sept. 2, 1947 2,604,464 Segall et al. July 22, 1952 2,646,417 Jennings Iuly 21, 1953 OTHER REFERENCES Alfrey et al.: Copolymerization Interscience, 1952, pp. 123, 124, 128, and 129. 

1. A TERPOLYMER PREPARED BY FREE-RADICAL-INITIATED BATCH POLYMERIZATION TO A CONVERSION OF AT LEAST 20 WEIGHT PERCENT OF A MONOMERIC MIXTURE CONSISTING OF (A) A MONOMER SELECTED FROM THE GROUP CONSISTING OF STYRENE, VINYLTOLUENE AND VINYLXYLENE, (B) ARYLONITRILE AND (C) A DIALKYL FUMARATE, THE PROPORTIONS OF THE THREE MONOMERS IN SAID MONOMERIC MIXTURE BEING LIMITED TO THOSE IN THE AREA OF MIXTURES THAT PRODUCE CLEAR TERPOLYMERS, SAID AREA ENCOMPASSING THE LINE JOINING THE POLYMERIZATION AZEOTROPE COMPOSITION OF THE PARTICULAR (A) AND ACRYLONITRILE ON THE ONE HAND AND THE PARTICULAR (A) AND ACRYDIALKYL FUMARATE ON THE OTHER HAND AS PLOTTED ON AN EQUILATERAL TRIANGULAR COORDINATE GRAPH. 